A telescopable vacuum-cleaner pipe of the type in which the invention is directed has been described in German patent 37 18 578, reference being had specifically to column 6, lines 49-65 of that patent.
In the system there described, the detent strip, i.e. the row of detent recesses and the slider which can be manipulated by the user are provided on diametrically opposite sides of the circumference of the vacuum-cleaner suction pipe.
For mechanical coupling of the slider and the retaining element which allows the displacement of the detent body, a stirrup is provided with two longitudinal shanks guided within a guide body filling the annular space between the cylindrical enlargement of the outer tube and the inner tube. The retaining element is displaced by this stirrup against a restoring force generated by two springs and which bias the retaining element into its retaining position. In the retracted position of the retaining element, against the force of these two springs, the detent body can disengage from a recess to allow telescoping displacement, i.e. relative axial displacement of the inner and outer tubes.
The telescopable vacuum-cleaner suction pipe of this system has the esthetic advantage that the detent strip is generally out of sight from the user because it is provided on the downwardly turned side or the underside of the pipe, i.e. the side opposite that at which the slider is visible.
However, the described construction is relatively complex and difficult to assemble.